Intel igb/e1000 driver showing dropped packets on the interface

Recently I ran into a strange issue where the Intel NIC was showing dropped packets on the interface. This particular server was having other issues (performance-ish type) so we were eager to get to the bottom of this.

Symptoms and interesting finds…

  1. ifconfig shows dropped packets only for RX
  2. The sum of rx_flow_control_xon+rx_flow_control_xoff from ethtool -S exatly matched #1 above. The count was reset at some point and we didn’t figure this out until later. Rebooting the server helped getting our minds clear and reset this.
  3. While tcpdump is running the dropped packet count would never increase.
  4. tcpdump wouldn’t show whatever was being dropped. I guess this is why they are dropped, no?

A solution, though not perfect was finally discovered. Disable BPDU/STP on the switch. The environment only had one switch so it wasn’t huge issue. On the Cisco the command was:

no spanning-tree vlan 1,100,168,216

Some interesting resources on this:

  1. Title : #477 igb driver, flow control packets being dropped?
  2. Title : Mystery RX packet drops on SLES11 SP2 every 30 sec


Windows Server 2008 SSL VPN (SSTP)

Now-a-days, every business is mobile, which means a VPN connection is most likely needed.  The problem is when clients travel to hotels or other countries, where firewall compatiblity and configuration can cause connectivity issues.  Fortunately, there is an answer for this: SSL VPNs.  Since an SSL VPN connection is secure and allowed on almost all firewalls, remote users will have a much more reliable connection mechanism; no matter where they are.  To top it off, SSL VPN (SSTP) is a feature natively bundled with Windows Server 2008.  How cool is that?

How does SSL VPNs help?

  • A NAT device doesn’t need to support PPTP in order for it to work.
  • Specific ports aren’t required to be open on the firewall (think hotels and other countries).
  • Connectivity can be made through web proxy servers.
  • The small footprint VPN client is easily accessible.

Clients supported: Vista SP1+, Windows 7, Windows Server 2008

What are the high level steps involved to setting up Windows Server 2008 SSL VPN connections (SSTP)?

  • Obtain a certificate to be used for your connections (just as if you are installing an SSL certificate for your website)
  • Install IIS on the VPN server
  • Request a certificate for the VPN server using the IIS Certificate Request Wizard
  • Install the SSL certificate
  • Install the RRAS server role on the VPN server
  • Enable the RRAS Server and configure it to be a VPN server
  • Configure the User Account to allow dial-up connections
  • Update DNS (ie.
  • Configure the Client to use SSTP and Connect to the VPN Server using SSTP

How-To configure Windows 2008 for SSTP VPN
1.  Install IIS on VPN server with all security settings marked for installation
2.  Create a Certificate Request in IIS console
a.  Make sure common name is actual Internet Hostname clients will connect to (e.g.
3.  Cut and Paste the certificate request into your SSL provider’s website
4.  Install any Intermediary certificates and your SSL certificate per your SSL provider’s instructions (DO NOT bind the certificate to a website in IIS)
5.  Install Routing and Remote Access
6.  Load the Routing and Remote Access MMC and run the wizard to enable it (Select Custom -> VPN if you are using only 1 NIC)
8.  Enable Dial-In access for the remote user’s AD account
9.  Enabled SSL connection (port 443) from the outside
10. Update DNS for the domain with the common name of the certificate
11. Test the SSL VPN connection by choosing SSTP in the vpn network connection properties

If the connection doesn’t work, make sure the proper certificate is bound following:
1.  Make sure the right certificate hash is bound (netsh http show  ssl)
a. If necessary, delete and readd the correct certificate binding…
1. Remove binding from IPv4 (netsh http delete ssl
2. Remove binding from IPv6 (netsh http delete ssl [::]:443)
3. Delete registry entry for the hash (reg delete hklmsystemcurrentcontrolsetservicessstpsvcparameters /v sha256certificatehash /f)
4. Add binding from IPv4 (netsh http add sslcert ipport= certhash=<replace with your cert hash> appid={ba195980-cd49-458b-9e23-c84ee0adcd75} certstorename=MY)
5. Add binding from IPv6 (netsh http add sslcert ipport=[::]:443 certhash=<replace with your cert hash> appid={ba195980-cd49-458b-9e23-c84ee0adcd75} certstorename=MY)

Helpful links to configuring SSTP VPN:

  • A step-by-step guide to setting up your own SSTP server is to be found here.
  • Troubleshooting help can be found here, here, and here.